Instructions:

Preheat a broiler. Place the beer, mustard, cayenne and Worcestershire
sauce in a saucepan, and heat over medium heat until boiling.
Slowly whisk in the cheese, making sure each addition is melted
before adding the next. Add the butter, and whisk until smooth.
Season with salt to taste, and set aside.

Place the tomato slices on the rack of a broiler pan, and
broil for 1 minute, or until lightly browned.

To serve, place the toast slices on the bottom of an oven­proof
gratin dish or in individual gratin dishes. Pour the cheese over
the toast, and then top with the tomato slices. Place under the
broiler and broil until the cheese is bubbly and brown. Serve
immediately.

Note: The components of the dish can be prepared up to
a few hours in advance and kept at room temperature. Reheat the
cheese until hot, whisking until it is smooth, before the final
broiling.